Canis Major and Canis Minor
are customarily associated with the great hunter, Orion, as his hunting dogs, following him obediently across the sky. Each of the constellations has but a single notably bright star: Sirius, the Dog Star, is well known as the brightest star of all (3½ times as bright as Arcturus, second ranked among northern hemisphere stars); and Procyon, the Before-Dog star, is well known, too, because it rises above the horizon just before Sirius does. Both of these stars are binary double stars, each with a white dwarf companion. Both are relatively close, 8.7 light years for Sirius, and 11 light years for Procyon. In fact, the only stars closer to the Sun than Sirius can be seen only from southern skies. Sirius has a diameter twice that of the Sun, while its companion Sirius B is tiny, only about three Earth-diameters in size, but nearly as massive as the Sun, many thousands of times as dense as either Sirius or the Sun. This interesting companion star was discovered in the year 1862 by the renowned telescope maker Alvan Clark while he was testing a new 18-inch refractor pointed at Sirius. It had previously been predicted that Sirius had a binary partner after the discovery in 1834 of a strange irregularity in its position. Although Sirius B is a respectable 8.4 magnitude star, its closeness to the brilliant Sirius makes it nearly impossible to detect with a telescope of less than 10 inches of aperture.

Sirius and Procyon are two of the stars that comprise the Winter Oval asterism. Some refer to this group of first magnitude stars as the Winter Hexagon, counting Pollux and Castor as a single corner of the shape. For those who may be unacquainted with this idea, the other stars, clockwise from Sirius and Procyon, are Pollux and Castor in Gemini, Capella in Auriga, Aldeberan in Taurus, and Rigel in Orion. A variant of this idea adds Bellatrix and Betelgeuse to this group, but omits Aldeberan, to form a giant figure 6 signaling a right ascension of 6 hours.

In the mythology of ancient Egypt, Osiris and Isis descended to the earth to bless the inhabitants. Isis showed them how to grow wheat and barley, and Osiris taught agriculture and also gave men laws and promoted the worship of the gods. He made the valley of the Nile a happy country, then he left his wife Isis in control of the government and set out to continue his good works in other lands. He conquered nations everywhere with music and eloquence, not with weapons. His brother Typhon became envious and plotted to kill Osiris through a malicious conspiracy. When Isis heard of the cruel murder she wept such tears that the Nile rose and overflowed its banks. From that time forward the annual rising of the Nile brought the life-giving renewal of fertility to the valley. Above, the star Sothis was identified with Isis, and this brilliant star (Sirius) was welcomed each year to herald the Nile flood. The day when it first was visible before dawn marked New Year’s Day, the most important day of the year. Temples erected to Isis were oriented to the exact spot where Sothis would rise. Sothis was the leader of 36 stars, called the Deccans, that followed each other at intervals of ten days throughout the year. By the heliacal rising of these stars, the Egyptians kept track of their calendar, adding five days to complete the year.

Of objects for viewing with binoculars in Canis Major and Canis Minor there are few. M41 is a beautiful open star cluster containing about a hundred stars. It is just visible to the naked eye and is just south of Sirius by four degrees. Stars of several different colors including some very red stars are in the field. R Canis Majoris is a variable star with a very short period, doubling its brightness from magnitude 6.7 to 5.9 in 27 hours. There are also some pretty double stars including the orange and pale blue h3945. Mu-Canis Majoris is a white-blue quadruple star.

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